In a transmitter/broadcast controlled subscription messaging system, the transmitted signal includes information which makes the message carried by the signal decodable or not decodable by a receiver, depending on subscription period information stored in the receiver. The subscription period information defines the period of time in months or years, from a particular start date, or until a particular expiry date, that the receiver is entitled to decode certain messages.
It is desirable to reduce the amount of information that needs to be transmitted in a subscription messaging system, and thus reduce the "air-time" for transmitting the information.